The present invention relates to an apparatus for recording an information signal using a rotating magnetic head, such as a VTR.
Since a video signal is recorded in a VTR as oblique magnetic tracks on a magnetic tape by a rotating magnetic head, it is required that tracking control be executed during the playback so that the rotating head correctly scans the video tracks.
For the tracking control, it is generally practiced that a control pulse is recorded in the recording at an edge portion of the magnetic tape by a stationary magnetic head at the rate of one pulse per revolution of the magnetic head and, in the playback, the travel of the tape, for example, is controlled such that the relationship between the played back control pulse and the rotational phase of the rotating head is kept identical to that in the recording. If servo control is executed in this way, the rotating head can correctly scan the video track.
In the modes of tape editing, there are an insert edit mode and an assemble edit mode. In either of the edit modes, the following steps are taken:
1 to rewind the tape from the edit starting point a length corresponding, for example, to three seconds, PA1 2 to start playing back the tape from the rewound position, with the playback kept in synchronism with the newly recorded video signal in the editing, and PA1 3 to switch the VTR from the playback mode to the record mode when the tape reaches the edit starting point,
By following the above procedure, no disarray of the track is produced at the edit starting point and, hence, no disturbance in the played back picture is caused there.
In actual practice of the tape editing under the described servo control, sometimes trouble is caused in the results of editing.
FIG. 7 shows a track pattern in a digital VTR. Referring to FIG. 7, reference numeral 1 denotes a magnetic tape and 2 denotes a magnetic track which is obtained in the normal recording. The track 2 is divided along its length into a track area 2S and a track area 2V, with an edit gap 2G provided between the area 2S and the area 2V. In this case, a digital audio signal is recorded and played back on the track area 2S and a digital video signal is recorded and played back on the track area 2V. The edit gap 2G constitutes a recordless area, i.e., a guard interval, between the area 2S and the area 2V.
(In actual digital VTRs, a digital video signal is divided into a plurality of channels and signals for the plurality of channels are recorded in a tape in the form of a plurality of tracks by a plurality of rotating heads in an inline array or a staggered array rotating as one body. However, since such details are not related to the essence of the present invention, the digital video signal is treated herein, for simplicity, as one channel of signal.)
When there are some errors in adjustment of the rotating head or the driving system of the tape 1, a rolling phenomenon of the rotating head in the recording, or expansion or shrinkage of the tape 1, the track 2 sometimes deviates from the normal position of the track 2 as indicated by broken lines in FIG. 7.
If insert editing of an audio signal is performed when there is such a deviation of the track 2, especially when there is some deviation of the track 2 in its longitudinal direction, it sometimes occurs, for example as shown in FIG. 8, that the newly formed track area 2S in the insert editing (indicated by broken lines) erases the front end portion 2Y of the track area 2V. When the tape with its track in such a state is played back, the played back video signal becomes deteriorated because the signal component corresponding to the portion 2Y cannot be obtained and, hence, the played back picture becomes disturbed.
Similarly, in insert editing of a video signal, if a new track area 2V formed by the insert editing is shifted to the side of the track area 2S, it sometimes occurs that the new track area 2V erases the rear end portion of the track area 2S. When the tape with its track in such a state is played back, the played back audio signal becomes deteriorated because the signal component corresponding to the erased portion cannot be obtained.
Further, if assemble edit of both an audio signal and a video signal is performed when there is some deviation of the track 2, it sometimes occurs that the tracks 2, in each assemble editing, deviate from the right position in their longitudinal direction as shown in FIG. 9. When a track is formed at the edge portion of the tape where the scanning by the head becomes unstable, it is difficult to playback the video and audio signals in a stable manner and sometimes tracking errors are produced and, hence, the played back audio signal is deteriorated or the played back picture disturbed.
When insert editing is performed on the tape 1 having the track pattern as shown in FIG. 9, there are sometimes produced unerased areas 2X as shown in FIG. 10. Also from such a state of the tape, deterioration in the played back audio signal or disturbance in the played back picture is produced.
Of course, such a thing that the front end portion 2Y of the track area 2V is erased or the rear end portion of the track area 2S is erased in the insert editing of the audio signal or the video signal will not occur in the above cases if there is provided a sufficient length of edit gap 2G between the area 2S and the area 2V.
In that case, however, the edit gap 2G must be given a sufficient length to provide for the worst case and, hence, the utilization factor of the tape 1 become worse. Further, when a plurality of channels of audio signal are arranged to be recorded and played back independently of each other, it becomes necessary, while providing the track area 2S for each channel, to provide edit gaps 2G between the track areas 2S. Then, the utilization factor of the tape 1 will become still worse.